11 research outputs found
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The meshing of timing belt teeth in pulley grooves
The work described here has been carried out to obtain a better understanding of the tooth root
cracking failure mode of timing belts. Previous work has demonstrated the close dependence of this on the
tooth deflections of fully meshed teeth, generated by torque transmission, but has not considered the
additional distortions generated in the partially meshed conditions at entry to and exit from a pulley groove.
Approximate compatibility and constitutive equations are combined with a rigorous consideration of tooth
equilibrium in partial meshing to show how bending moments are generated at both exit from a driven
pulley and entry to a driving pulley. Experimentally determined belt lives correlate very well with a
combined measure of fully meshed tooth strain and strain due to bending at entry or exit. The analysis also
shows that this strain measure reduces with increasing belt tooth stiffness, confirming the importance of a
high tooth stiffness for a long belt life. Tooth force variations through the partial meshing cycle have also
been predicted and compared with measurements obtained from a special strain gauge instrumented pulley.
A greater pulley rotation than is predicted is required for a belt tooth to seat in a pulley groove. There is
room for improvement in the modellin